The US government has acknowledged that a US citizen has been arrested in Iran. Friends and family say Siamak Namazi was taken into custody on 15 October.
Photograph: Courtesy of Siamak Namazi

A businessman based in Dubai has reportedly become at least the fourth Iranian American to be detained in Iran, family and friends say.

People close to consultant Siamak Namazi have told media outlets that he was taken into custody by Iran’s security forces around 15 October while visiting family in Iran.

“We’re aware of recent reports of the possible arrest in Iran of a US citizen,” said US Department of State spokesman John Kirby. “We’re looking into these reports and don’t have anything further to provide at this time.”

Namazi, who supports improved diplomatic relations between the US and Iran, is the head of strategic planning at Crescent Petroleum. He previously worked as an energy consultant at the Dubai-based Access Consulting Group and at numerous thinktanks.

The National Iranian American Council, which also supports the easing of relations between the two countries, said in a statement that it was “deeply troubled” by the unconfirmed reports.

It also disputed claims by other websites that said Namazi and his family have leadership roles in the organization. “While Mr Namazi has known members of NIAC’s staff, neither he nor his family have had any leadership or any other significant role with NIAC,” the statement said.

While Iran’s moderate president Hassan Rouhani has expressed interest in easing US-Iran relations, Iran’s supreme leader Ayatollah Ali Khamenei has made clear that he does not think improved relations should come with the historic nuclear deal reached in July.

Namazi’s affiliates told the Wall Street Journal that he was arrested by the Revolutionary Guard Corps intelligence arm, which is under the supervision of Khamenei, not the government.

Hadi Ghaemi, the executive director of the International Campaign for Human Rights in Iran, said that the detention feeds into an emerging pattern of the Revolutionary Guard targeting the Rouhani government’s economic policies in the wake of the historic nuclear deal reached in July.

This also comes ahead of the February parliamentary election in Iran.

“I read this as an attempt to undermine Rouhani’s policy of jumpstarting the economy through interactions with the diaspora,” said Ghaemi. “And of course this will politically weaken him in light of the upcoming election because he will not have much economic benefit to show to the people.”

At least three other Americans – Amir Hekmati, Saeed Abedini and Jason Rezaian– are being held in Iranian prisons. Their families hoped that a release could be secured with the nuclear deal, but officials have said they deliberately kept those negotiations separate from the nuclear talks in case the deal fell through.

Iran does not recognize dual citizenship, and those that hold it are viewed with suspicion.

US secretary of state John Kerry mentioned the detained Americans in a meeting with Iran foreign minister Mohammad Javad Zarif earlier this week in Vienna, where he is in discussions with Iranian diplomats about the Syrian war.

The state department on Fridaysaid Kerry raised the issue of detained and missing US citizens in the country but did not provide further details on the conversation.

Kerry and Zarif’s meeting in Vienna came just two weeks after Rezaian, a Washington Post correspondent, was convicted in a secret espionage trial in Iran. He has been imprisoned in Iran for more than 450 days.

Former US marine Amir Hekmati has been held in Iran since his arrest there in August 2011 and Christian pastor Saeed Abedini is also jailed in an Iranian prison. The US is also looking for former FBI agent Robert Levinson, who disappeared in the country in 2007.

IranWire first reported the arrest of an unnamed Iranian American earlier this month and on Wednesday edited the story to say the person they referenced is Namazi.

The reports came as Washington-based group IJMA3-USA, an internet freedom advocacy group, said its secretary general, Lebanese citizen Nizar Zakka, disappeared in September while attending a conference in Tehran.

“We have filed several requests with the Lebanese Ministry of Foreign Affairs asking assistance in locating him, without success,” the group said in a statement signed by lawyer Antoine Abou Dib. “We therefore respectfully ask the Lebanese Ministry of Foreign Affairs, the Lebanese Embassy in Tehran and the Iranian authorities to assist us in locating Mr Zakka, and to confirm that he is safe and will soon be permitted to return home.”

Zakka was last seen in a taxi bound for the airport for a flight to Beirut. Abou Dib said that he did not board the flight.